The effect of soil temperature, sowing depth and soil bulk density on the seedling emergence of tall fescue (Festuca arundinacea Schreb.) and white clover (Trifolium repens L.)

Abstract

The effects of temperature (constant 3, 6, 9, 12 and 24�C, and an alternating 6/12�C temperature regime), sowing depth (0, 15, 30 and 45 mm), and soil bulk density (1.1 and 1.3 g cm-3) were examined on the emergence of tall fescue (Festuca arundinacea, cv. Demeter) and white clover (Trifolium repens, cv. Haifa) in a factorial experiment, in controlled temperature cabinets. Mitscherlich curves were fitted to the emergence data and treatment effects on the maximum emergence percentage (A), rate of emergence (K) and time to first emergence (To), were statistically analysed. Temperature was the major factor affecting the fescue A value. The A value was low at 3 and 6�C, but increased as temperature increased to 12�C. It was depressed by the 45 mm sowing depth and by high bulk density at 30 and 45 mm. For white clover, sowing depth had a strong effect on A. Over all temperatures, A was high for surface sowing and low for deeper sowing (30 and 45 mm). For shallow sowing (15 mm), A was intermediate and increased with rising temperature. High bulk density depressed A at 15 mm. For both species, To increased as sowing depth increased, and decreased as temperature increased. The effect of sowing depth was more apparent at low temperatures. The K value for fescue increased gradually as temperature increased, but sowing depth had no effect. For clover, K increased markedly with rises in temperature for surface sowing, with smaller increases for 15, 30 and 45 mm depths. The 6/12�C regime responses for A and To were similar to the constant 12�C, while the K response was similar to the constant 9�C; these trends were similar for fescue and clover. It was concluded that establishment failures from direct drilling tall fescue on the Northern Tablelands can be related to low soil temperatures in winter (below 9�C), and for white clover, to excessive sowing depth (greater than 15 mm), particularly on high bulk density soils.